Apparatus for solidifying and pressing carbon dioxide and the like



A. SCHUTZv Jan. 24, 1939.

, APPARATUS FOR SOLIDIFYING AND PRESSING CARBON DIOXIDE AND THE LIKE 2 Sheets-Sheet l Filed Feb. 3, 1936 Jan. 24, 1939. A. SCHUTZ 2,145,096

APPARATUS FOR SOJIIDIFY'ING ANU PRESSING CARBON DIOXIDE AND THE LIKE y Filed-Feb. 5, 1936 2 sheets-shane Patented Jan. 24, 1939 ITED STAT-as PATENT OFI-ice -PPARATUS FOR SOLDIFYING AND PRESS- ENG .CARBON DIOXIDE AND THE LIKE Adolph Schutz, Wurzen, Germany, assigner, by mesne assignments, to International Carbonio .I Engineering Company, Wilmington, Del.`

InGermany February 12, 1935 Application February 3, 1936, Serial No. 62,209

2s claims. (c1. ca -121) This invention relates to certain improvements in apparatus for solidifying and pressing carbon dioxide and the like, and the nature and objects of the invention will be readily recognized and 5 understood by those skilled in the art in the light of the following explanation and description of the accompanying drawings illustrating what I now believe to be the preferred embodiments or mechanical expressions of my invention from o among various other embodiments, arrangements,

designs, constructions and combinations of whichthe invention is capable within the spirit and scope thereof.

solidified carbon dioxide is now in i. wide com-- tity or mass of such snow is then-compressedA or compacted, usually by mechanical pressing apparatus, into dense, coherent form as a block or 5 cake capable of structurally withstanding handling and transportation in use.

Attention is here directed'to the fact that the term "snow as used herein is to be interpreted in a broad,'generic sense to include the carbon 3o dioxide in its solidified form prior to any pressing `or compacting of a mass thereof into a more dense and coherent block or cake form; and is not used in the more limited or strict sense of the small crystal or snow-flake forms resulting from certain I 35 methods of carbon dioxide solidiilcation.

T he solidication of the carbon dioxide is mainly carried out commercially in two general types of apparatus, in one of which the solidiflcation takes place in the actual pressing chamber 40 of the press apparatus, while in the other type solidication is-carried out in a separate chamber in gas-tight communication with the pressing chamber so that the solidified carbon dioxide may pass from the solidicationchamber to the pressing chamber. My present invention relates to the latter type of apparatus and is directed toward increasing the eiciency of thetype and providing a design and arrangement of apparatus for continuousl operation with simultaneous 5o solidication and pressing..

As a factor in the problem of simultaneous solidiiication and pressing to'attain continuous operation of such apparatus, experience has demonstrated the necessity for carrying out the 55 pressing of a mass oi' SOlidfled $231911 dioxide in collects in the chamber.

a pressing chamber with the chamber at substantially atmospheric pressures and with practically all carbon dioxide gas removed from the chamberA before pressing, in order to avoid occluding gas in `the block of carbon dioxide produced. If gas is compressed or occluded in the completed block, 5

y then when the block is removed from the apparatus` at atmospheric pressure, such gas tends to expand and escape from the block with such force as to disrupt the block or impair its coherency lo and structural strength.

The solidiiication of the carbon dioxide in the solidication chamber of such types of apparatus is generally carried out by expanding liquid carbon dioxide in the chamber to a pressure below the triple point while withdrawing the resulting-expansion gas from the chamber, so that a portion of the liquid is frozen out into solidied form and As a result of the liquid expansion in the .chamber and gas Withdrawal there is established a certain gas velocity in the chamber and a certain part of the solidified particles may become 4entrained in the gas and be withdrawn with the gas from the chamber. 'Ihe extent of such entrainment and the resulting amount of lsolid withdrawn would appear to be 1 dependent upon the gas velocity established in the chamber and the higher the velocity the greater the entrainment and consequently the larger the quantity of solid that may be with- 30- drawn from the chamber.

The gas velocity in a given solidiflcation chamber is mainly determined by the cross sectional area of the solidiflcation chamber, the rate at which the liquid is being expanded in the cham-v ber, the pressure` of the liquid before its expansion into the chamber, and the pressure in the chamber down to' which the liquid is expanded. Thus, by increasing the cross sectional area of the chamber, or by'decreasing the rate of ex- 40 pansion of the liquid into the chamber, or by-both these changes, the velocity of the gas in the vchamber can be lowered and the possibility of solid entrainment reduced. However, in commercial operation it is desirable from the economy and emciency standpoint, to produce in a given time as much solid as possible by expanding the liquid carbon dioxide at as high a rate as possible, so, that the lowering of gas velocity in the solidification chamber by reducing the rate of liquid 50 expansion is not generally practically feasible or desirable.

With the type of apparatus having the separate solidication chamber, in order to obtain the de- Sil'ed free passage or transfer of the solidied 55 a practical apparatus may not be increased in order to lower chamber gas velocity but should be the same as the pressing chamber. As low gas velocity is desired, then the cross sectional area of the soli-diflcation chamber is made as large as possible within the stated limits, that is, a cross section the same as that of the pressing chamber.

It has been established that the gas velocity in a given solidication chamber decreases with a decrease in the pressure differential between the initial pressure (which must be above the triple point) at which the liquid or fluid carbon dioxide is admitted to the solidication chamber, and the pressure maintained in the chamber during'admission (which pressure must be below the triple point) and down to which the carbon dioxide is expanded to produce a por-tion thereof in the solidied form. Thus, with a solidification chamber of given cross sectional -area with a given rate of liquid expansion, by lowering the pressure of the liquid'carbon dioxide toward the triple point prior to admission to the chamber and by raising the chamberpressure toward the triple point, thereby reducing the pressure differential, the gas velocity in the chamber may be reduced during solidication without either increasing the cross sectional area of the cham` ber or reducing the rate of liquid expansion and` production of solid.

In solidifying and pressing apparatus of the general types'under discussion, experience has shown that when all of the foregoing factors are' set for the most efficient practical operation, the rate at which the solidified gas can be pressed in the pressing chamber is much higher than the rate at which the solidified gas can be generated or produced in the solidication chamber, so that, in. practice it is found vthat with the solidification chamber operated at its maximum rate of production, the pressing chamber can only be operated to press the solid at about one-half, or even less, the rate of which it is capable.

My present invention is primarily directed to the provision of carbon dioxide y and the like -solidication and pressing apparatus of the types having a solidication chamber separate from a pressing chamber, with which apparatus continuous production of blocks of solidied carbondioxide can be carried out with simultaneous solidication and pressing,` and by which the pressing as well as the solidification can be performed at the maximum rates of production of which the solidication chamber and pressing chamber or unit of a given apparatus are capable.

-A further aim and feature of the invention is to provide such an apparatus for continuous and simultaneous solidication and pressing at max- 1mum production rates, with which solidiflcation methods may be carried out which require the maintenance of above atmospheric pressures in the solidication chamber during solidication,l yet which apparatus can be operated for simultaneous solidication and pressing while eliminating above atmospheric pressures in the pressing chamber and the resulting occluded gas foregoing general object of simultaneous solidification and pressing with continuous solid carbon dioxide block production, resides in the provision of a design and construction of apparatus in which a single press unit is supplied with solidified carbon dioxidev from a plurality of solidication chambers in such a manner that the pressing chamber can be maintained substantially free of gas and at atmospheric pressures without interrupting the production' of solid carbon dioxide in the solidiiication chambers, and the press unit can be continuously operated to press the solidified carbon dioxide into blocks without interruption due to the solidification of the carbon dioxide in the solidiflcation chambers or transfer` of such solid to the pressing chamber.

A further feature of apparatus .of the invention is embodied in the arrangement of the solidication chambers and the pressing chamber -of the press unit, by which the solidification chambers. are maintained closed to the latmosphere at all times during solidiflcation therein and transfer of solidtherefrom to the pressing chamber of the press unit; `and by which thepressing chamber is maintained closed to atmosphere during charging with'solid and pressing of such solid therein.

A further feature of the invention is found in the arrangement for transferring measured charges of solidified carbon dioxide from a plurality of solidiiication chambers to the pressing chamber of a single press unit associated with such solidication chambers to form a solidification and pressing apparatus in accordance with my' invention.

An object of the invention is also to provide a p' practical and efficient design and construction of apparatus embodying the foregoing general features and for attaining the results generally re. ferred to, which design and construction is mechanically simple and of relatively low cost to build yet will be capable of eflicient operation under actual production conditions.

With the foregoing general features, objects and results in view, as well as certain others which or less diagrammatic, through a solidifying and.

pressing apparatus of the invention, and showing solidication taking place in one of the solidi'cation chambers, while the other 'chamber is filled with solid, and also showing the press unit in position for receiving a measured charge of solid' from the filled solidication chamber.

Fig. 2 is a view similar to Fig. 1, but with the movable transfer chamber unit in position discharging a charge of' solid from the inactive solidipreceding views but showing the next charge of solid discharged from the transfer chamber into the intermediate chamber and held therein by the press chamber closing head, while the press unit is in completed block ejecting position.

On'e possible form of apparatus for carrying out and practically embodying the principles and features of the invention is disclosed in the accompanying drawings, and includes in accordance with the fundamentals of the invention, a plurality of separate carbon dioxide or other gas solidification chambers, in this instance consisting of the two chambers SL and SR, associated with a single press unit P through the medium of an intermediate solidied gas measuring and charge receiving chamber M, and the charge transferv chamber units TL and TR. Such major elements are combined into the apparatus by which the gas is solidifled and charges thereof are transferred from the solidification chambers to the.

press unit in such` a manner that solidiflcation can be continuously carried out and the press unit supplied with solidied gas during uninterrupted operation 'of the press unit.

In the particular design and arrangement of the present example of apparatus, the press unit VP includes a base I having the vertically disposed, upwardly extending concentric inner and outer uid pressure cylinders and I2 mounted thereon, with the pressure actuated pistons |4 and I respectively, slidably mounted for reciprocation therein. The inner uid pressure cylinder |I is-provided with the pressure uid passages Ila and `Hb in communication therewith at opposite sides of the piston I4, while the outer cylinder I2 is provided with the fluid pressure` passages 2a and |2b opening thereinto at opposite sides of its piston I5, referring particularly to Fig. 1 of the drawings.- Y n 'I'he cylinders II and I2 are connected through their respective passages IIa and I-Ib and I2a and |2b, with any suitable source of fluid pressure not shown) for control of such pressure to the cy inders in the usual or any desired manner to raise and lower the pistons I4 and I5 under the required pressures. It is not deemed necessary to here disclose such a source of uidpressure or anyfcontrol means for actuating the pistons I4 and I5, in view of the factthat any of a variety of known arrangements may be employed, and the means for operating and controlling the pistons I4 and |5'forms no part of the invention hereof. e

The piston I5 of the outer cylinder I2 is of annular or ring form concentricwith. and' slldably engaging the outer wall surface of the inner cylinder II, and is provided with an upwardly extending sleeve I6. The 4press cylinder I1,

vwhich provides the solidified gas pressing chamber, is in this instance directly carried on and as an upward continuation of the upwardly extending sleeve |6 of piston I5. 'I'he piston I4 in the inner cylinder is provided with a piston rod I8 that extends upwardly therefrom and outwardly through the closed upper end or head lof cylinder II in which it has a sliding and sealing fit, and this piston rod is in axial alinement with the press cylinder I1. A pressing head or plungsr I9 is mounted on-the upper end of piston rodl I8 and is slidably received in and forms the lower end closure for the press cylinder I1, so that the plunger I 9 is reciprocal in cylinder I1` by the uid pressure actuation of piston I4, and/or by relative movement between press cylinder I1 and its pressing plunger I9.

The press cylinder I1 is raised and lowered by the fluid pressure actuated piston I5 in cylinder I2, independently of the actuation of plunger I9 by piston I4, and it is to be noted, by reference to Fig. 4`of the drawings, that with the press cylinder I1 and its pressing plunger I9 both in their lower-most positions, the plunger I9 is positioned at the upper end of the press cylinder with its upper surface at least ush with the upper edge ofthe cylinder or even above the press cylinder upper edge. In raised position of the press cylinder I1 and lowered position of plunger I9, the latter is positioned in the lower end of the press cylinder for upward movement by piston I4,v in

the press cylinder to press a mass or charge of upper end and at its lower end opens into a transverse, horizontal slideway 2| formed in the housing structure 20. The chamber Mis vertically axially alined with the press cylinder |1 and has vthe saine internal diameter as that of the pressing chamber formed by the press cylinder. At the lower or under side of slideway 2|, the housing structure is provided with a vertical opening or passage 22 there-through axially alined with chamber M and of a diameter to receive and seat the upper end of press cylinder I1 -when the latter is in the raised charge receiving and pressing positions of Figs. 1 to'3. The upper end of press vcylinder I1 has areduced diameter in the example hereof to form a shoulder Ila (see Fig. 4) which may if desired engage the under side vof structure 20. Y.

A slide or gate .valve 23` is slidably mounted and confined in slideway 2| of structure 20, and

includes a vertical port or opening 24 therethrough having a diameter equal to the internal diameter of press cylinder I1 and charge receiving and measuring chamber M. vThis, slide 23 is movable in slideway 2| to the position shown rin Figs. 1 and 2. in which its port 24 .is alined with chamber M and the open end of press cylinder I1, so that there is formed a continuous,

unbroken passage through chamber M and port 24 into the press cylinder. Preferably, the slide 23 'forms a substantially sealing iit in its slidef way, and the upper end of press cylinder |1`in raised position forms a substantially sealed fit in opening 22, so that the chamber M, port 24 and press cylinder chamber when together as shown in Figs. 1 and 2, form a chamber or space substantially closed to atmosphere. From position placing chamber M and the pressing cham'- ber of cylinder I1 in communication, the slide 23 ismovable, to the left in Figs. 1 and 2, to remove port 24 from connecting alinement between chamber M and press cylinder I1, and to place the slide in position closing and shutting of! the chamber M and press cylinder from each other,

while forming a closure head for the upper end i with a piston rod 21 extending therefrom to and operatively connected with the slide. The cylinder 25 is formed with the pressure fluid passages 25a and 25h (see Fig. 1) thereinto at opposite sides of piston 26, which passes are connected with a source of fluid pressureand are opened and closed in the usual manner, to cause piston 26 to move slide 23 to the desired positions.

The gas solidication chambers SL and SR are supported in vertical position spaced above str'ucture 20 on a base 30 which is fixed in position spaced above and parallel with the upper side wall 20' of the lower housing structure 20 by suitable end walls 3|, an'd if desired spaced side walls (notshown), to form a slideway therebetween for the movable transfer lchamber units 'I'L and TR. The solidif'lcation chambers SL and SR are in the example hereof, of elongated tubular form and are mountedspaced apart on base 30 at diametrically opposite sides of and spaced equal distances from the measuring or` charge receiving chamber M in the housing structure 20. The solidiflcation chambers are mounted and secured'in suitable openings in the base 30 and are open at theirlower ends into the slideway formed by and between wall 20' and the base 30.

The transfer chamber u nits TL and TR are each formed by a cylinder or tubular structure that provides a vertical open ended chamber therethrough and are of a height or depth equal to the space'between the wall 20 and solidification chamber supporting base 30. The units TL and TR are mounted in the space between wall 20 and base 30 -to form a freely sliding but preferably sealingengagement at their upper and lower sides or ends with the inner surfaces of the base 30 and wall 20. respectively, so that the units may be slid or moved between the solidification chambers and the charge receiving chamber M. In normal inactive position the transfer chamber units TL and TR, which have internal diameters equal to the internal diameters of the solidification chambers, are in positions beneath and vertically alined with the chambers SL and TR, respectively,so.that the open upper ends of the transfer chambers register and join with tions of. and receive material from the solidiflcation chambers, as shown in Figs. 1 and 3 of the drawings. The lower open ends 'of the transfer chamber units TL and TR when in theforegoing positions are closed by the wall 20 forming the lower track of the slideway for the units Each transfer chamber unit TL and. TR is formed with a horizontally disposed closure plate 32 extending from the upper side thereof 'outwardly toward the adjacent outer end of the slide Way, and these closure plates form a sliding and preferably sealing engagement with the under surface of the base 30 which forms the upper track of the slideway.

Each of the sliding transfer units TL and TR is operatively coupled with a means for moving the unit'between position alined with a solidica-m fluid cylinder 25 mounted at one tior'i chamber and position alined with the charge receiving chamber M. In the present example operated type and for each unit comprise a uid pressure cylinder 33 mounted in the end wall 3| o f the slideway adjacent the respective transfer chamber unit, and extended a distance into the slideway. Each cylinder has a piston rod 35 extended to and connectedwith the piston so that by reciprocating the piston the transfer unit with which it is coupled ismoved between a -solidiflcation chamber and the chamber M. 'Ihe transfer chamber units are connected with a source of fluid pressure and means (not shown) are provided for controlling the pressure uid and admitting it to the cylinders to reciprocate pistons 34 to obtain the desired movement and position for the transfer units, as will be readily undery stood by those skilled in the art.

The gas solidificationch'ambers SL and SR are 'connected with asourceof liquefied gas, which for the purposes of the-present example is a source of liquefied carbon dioxide, and each is providedl 'with a suitable pipe or nozzle I0 for discharging the liquefied carbon dioxide into the chamber for Aexpansion and conversion of a portion of the liquid to solid carbon'dioxide or "snow", and the remainder to gaseous carbon dioxide. The upper end of each chamber is also provided with a gas withdrawal or oftake conduit 4| through which the expansion gases are withdrawn from the chamber.y The liquid carbon dioxide is supplied to the discharge or nozzle 40' of a solidiflcation 4 liquid at this reduced pressure is then discharged into the solidiflcation chamber in which a pres-- sure is maintained above atmospheric, say, of the order of approximately 3 atmospheres, so that the liquid is expanded to a pressure below its triple point of 4.28 atmospheres (5.28 ats. absolute) with the resulting freezing out of a portion of the liquid as solid while the remainder gasifies.V The solid is collected in the chamber and the expansion gases are -withdrawn from the chamber at a rate in relation to the liquid discharge rate, and other controllingA factors, to maintain the required pressure of the order of 3 .atmospheres in the solidification chamber. By such method not only is there a greater percentage of solid such actuating means are of the fluid pressure obtained from the liquid due to .the lowered teml e perature from the pressure reduction of the liquid, but also by reducing the pressure differential between the chamber or solidi'cation pressure and the liquid pressure, the gas velocity in the chamber is lowered and the tendency of the Withdrawn gas to carry off particles of the solid or snow by entrainment is thereby reduced.

With such methods of solidiflcation it has been found in practice that the liquid carbon dioxide cannot be safely reduced in pressure below a gauge pressure'of the order of about 7 atmospheres, and in fact a minimum pressure of the order of 8 to 81/9i atmospheres with anormal working pressure of about 9% to l0 atmospheres may be said -to be preferable. The lower pressures stated above may be successfullyv used with a animeeA plant in continuous operation, but the higher pressures should be employed when the plant is working intermittently. Obviously, a minimum pressure must be employed for the liquid that is sufficiently above the triple point to provide a margin of safety for a fall or drop in pressure in the liquid line, such as might be caused by a leali or resistance to liquid flow. Upon such a fall in pressure a part of the liquid will expand and if the triple point is reached solidication of a part will result tending to cause the liquid line to freeze up.

With respect to the above atmospheric pressure in the solidication chamber, such pressure must of course be maintained below the triple point pressure of 4.28 atmospheres, gauge, and experience has shown that suchpressure may not practically approach too close to the triple point. If the pressure is too close to the triple point in a process operating at high speed there is the possibility of carrying some unexpanded liquid into the solid and if the solid be immediately pressed with such liquid present, there would be occluded gas in the pressed block. For such reason, the maximum solidification chamber pressure in practice should preferably not exceed a gauge pressure of the order of 3 atmospheres, and

may even beof the order of2 atmospheres.

- oitake lines 4I SL and SR are connected with the intake of a gas Vcompressor (not shown) or other source to which The expansion gas withdrawal conduits or gas from the solidication chambers the gaseous carbon dioxide from the solidication chambers is withdrawn, and may be then recompressed and reliqueed for return to the solidication chambers as liquid for further expansion and solidication.

With the solidication and pressing apparatus of the embodiment hereof in operation and carrying out the carbon dioxide solidication method as described, referring now to Fig. 1 of the drawings, the transfer chamber units TL and 'I'R are moved to and held in the positions alined with and forming the lower end portions of chambers SL and SR, respectively, with the lower ends o f the transfer units, that is to say,. the solidication chambers, substantially sealed and closed to atmosphere by the upper wall 20' of the housing structure 20. Liquid carbon dioxide at the reduced pressure of approximately 8 atmospheres has been expanded into solidication chamber SR in which the pressure'has been maintained at approximately 3 atmospheres, and the resulting solidified carbon dioxide has been collected in the chamber formed by the transfer' chamber'IR and solidication chamber SR, while the expansion gas has been withdrawn through conduit 4I until the chamber is substantially filled with solid or snow as indicated. When filled the liquid supply line is shut olf by valve 43, and the pressure in the chamber is allowed to fall to atmospheric and the mass 4of more or less loose crystals of the solidified carbon dioxide is ready for transfer to the press unit P.

The -solidiication chamber SL, which may have been emptied ofits solid, is again being charged with solid by maintaining the above atmospheric pressure therein of.approximately 3 atmospheres and discharging the liquid carbon dioxide at a reduced pressure of approximately 8 atmospheres through discharge pipe 40 into the chamber while withdrawing the expansion gas through conduit 4I. At this point attention is called to the fact' that while the particular method of solidifying carbon dioxide of the invention isdescribed the chamber M and is as employed in lling the solldiiication chambers of the apparatus, and while such method may be preferred, yet the apparatus of the invention is not limited to use with such method, and any other desired or suitable solidiflcation method for While the chamber sL is being uned, the nued chamber SR in which atmospheric pressure preferably prevails, is to have its solidified. carbon dioxide transferred to the press unit P. The press cylinder I'I is raised to position of Fig. 1 by the iiuid pressure piston I5, with its open upper end received in passage 22 and thus placed in direct unobstructed communication with Ichamber M through port 24 of slide valve 23, which latter is moved to position registering port 24 with chamber M and the raised press cylinder by fluid pressure cylinder 25. The pressing plunger I3 is maintained in its lowered position at the lower end of and closing the press cylinder chamber preparatory to receiving a charge of solidied carbon dioxide in the press cylinder.

With the elements of the press unit so positioned, the transfer chamber unit. TR, which is lled. with a charge of solidied carbon dioxide, is moved by its actuating piston ,33 i'n the slideway into registration with the intermediate or measuring chamber M rand the charge of solid in -the transfer unit falls by fgravity through chamber M- and port 24 into the pressing cylinder I'I, as clearly shown by Fig. 2- of the drawings.

As the transfer unit TR is moved from alinement with the lower end of chamber SR, the closure plate 32 carried by the unit, slides across 'and closes the lower` open end of the solidication charge to chamber` M. While the transfer unitv TR is being returned to and lled from chamber SR, the pressing plunger I9 is forced upwardlyv by the fluid pressure piston I4 in cylinder II under sufficient pressure to press the charge of solidied carbon dioxide in the pressing cylinder against slide 23 which forms the closure head for the press cylinder, into a dense block .Bof solid carbon dioxide as shown in Fig. 3 of the drawings.

Meanwhile, the charged transfer unit TR is again moved into alinement with chamber M, the lower end of solidication chamber SR being closed by plate 32, and its charge is dropped into held therein on slideM which closes the lower end of this chamber, preparatory to movement into the pressing chamber y of pressing cylinder II, as will be clear by reference to Fig. 4.

Upon .completion of the block B in the upper end of press cylinder I'I, as shown in Fig. 3, the

' press cylinder is lowered with the pressing plunger I9, by operation of iiuid pressure cylinders I2 and Il, but as the downward movement of the press cylinder is greater than the downward movement of the pressing plunger, such cylinder moves downwardly past and relatively to the plunger after the latter has reached its down- `ward limit of movement, so that the block of solidified carbon dioxide B is in effect ejected 4from the pressing cylinder and exposedsupported on the upper end of the plunger I9 for ready unobstructed removal from the apparatus. The foregoing block ejecting position of the press cylinder and plunger of the press unit P is clearly shown in Fig. 4 of the drawings.

Upon removal of the completed block B from the apparatus, the pressing cylinder I1 is again raised to charge receiving position of Fig. 1, and the slide 23 is moved to register its port 24 with pressing cylinder I1h and intermediate chamber M, so that, the charge, of solidiedcarbon dioxide previously transferred to and held in chamber M, is released and falls into the charges the Y pressing cylinder to be pressed therein into a block by the pressing plunger, in the manner above explained. The sequence of operations of transferring charges from solidication chamber SR to chamber Mand the pressing cylinder, by transfer unit TR, and the pressing of such charges into blocksis continued until the mass of solidI in chamber SR has been transferred charge by charge to the press unit P and converted into blocks. The transfer of the solid from the solidification chamber SR and the pressing of the solid into blocks is carried out with the solidification chamberl and the pressing chamber at substantially atmospheric pressure, and with substantially all'of the carbon dioxide gases removed from the solidication chamber, so

that, the occluding of such gas into the blocks is practically eliminated.

The solidication of the carbon dioxide in the chamber SL is carried on during the transfer of the mass of solid from the inactive chamber SR to the press unit P, and the chamber SL will be filled and prepared to supply solid to the press by charge to the press unit P, by its transfer unit.

TL, and converted into blocks in the same manner and by the same series of operations as described in connection with solidication chamber SR and its transfer unit TR.

Thus, with the apparatus of the invention 'solidication is continuous-and block pressing is continuously carriedv out by a single pressing unit during solidication and Without interrupting the pressing operations because of solidication and the conditions established thereby. The Vuse of alternate solidication chambers for solidication and for transfer of solid to the press unit enables the use of any desired and advantageous solidication methods, irrespective of pressures used, and also permits of the transfer ofthe solid from a solidication chamber to the pressing chamber at atmospheric pressures and with substantially all expansion gas removed so as to reduce and/practically eliminate the difliculties of occuluded gas in the completed blocks. The transfer of measured quantities of the solidied gas to the press unit, under the above conditions, also materially contributes to the uniform character of the blocks produced by the apparatus.

The example of apparatus of the invention illustrated and described herein, included but two solldication chambers, but the invention contemplates and includes any desirable number, with a transfer unit for each chamber, or with one or more transfer units serving a greater number of chambers.

It is also evident' that various other changes, modifications, variations, additions, eliminations and substitutions might be resorted to without departing from the spirit and broad scope of the invention, and hence I do not wish to limit the invention in all respects to the exact and specific disclosures hereof.

1. An apparatus for gas solidiiication and pressing, including inoperative combination separate sources of solidified gas, a press unit in normal fixed position relative to said sources, said unit including a pressing chamber for receiving a charge of solidified gas and pressing the same therein into a block, and a charge transfer unit for each Vof said sources movable between the source and the press unit for transferring a solidified gas charge from the source to the press chamber of the unit.

2. In apparatus for gas solidication and pressing, the combination in operative assembly o f a plurality of separate gas solidiiication chambers, a solidied gas charge receiving chamber spaced from said solidication chambers, and transfer units movable between said solidification chambers and said receiving chamber for transferring a charge of solidified gas from any one of said solidication chambers to said receiving chamber, in combination with apress unit for receiving a charge of solidified gas from the receiving chamber to press such charge into a block.

3. Apparatus for gas solidification and pressing including in combination and operative assembly, separate gas solidification chambers, a press unit including a solidified gas charge receiving and pressing chamber spaced from said solidication chambers, a charge transfer unit for each solidication chamber movable between position receiving a charge from its solidification chamber to position -for discharging such charge 'into the pressing chamber of said pressing unit,

and means for actuating said transfer units.

4. Apparatus for gas solidification and pressing, including in combinationand operative asa sembly, separate gas solidication chambers, a

including a solidied gas charge pressing chamber for'charge receiving association withsaid holding chamber, a charge transfer unit for each solidication chamber movable between a position receiving a r charge from a solidication chamber and a position discharging such charge into the pressing chamber of the press unit, and means for selectively actuating said transfer units.

5. In gas solidication and pressing apparatus, a solidication chamber, a solidified gas charge receiving and -holding chamber remote from the solidication chamber, a pressing chamber having a pressing plunger therein for pressing a charge of solidified gas into a block, said pressing chamber associated with said holding chambei' for receiving a charge of solidified gas therefrom, means for opening and closing communication between the holding chamber and the pressing chamber, said means in closing position forming chamber is pressed by said plunger, and a open ended .vertical chamber, a transfer unit for receiving a charge of'solidiled gas from the solidication chamber, said transfer unit in charge receiving position forming a portion of the -solidication chamber and movable from the chamber to a position for Vdischarging the charge to the pressing chamber of the press unit, and means for closing the solidication chamber when said transfer unit is moved from charge receiving position.

'7. In gas solidiflcation and pressing apparatus, a gas solidication chamber, a solidified gas pressing chamber spaced from the solidication chamber, one end portion of the solidiflcation chamber formed by a movable charge transfer unit, a slideway in which .said unit is mounted, said transfer unit movable in said slideway from the solidificationchamber to a position for discharging a charge of solidified gas to the pressing chamber, said transfer unit closed by said slideway during movements-between charge receiving and charge discharging positions, and a closure member carried by said unit for closing the solidification chamber when the transfer unit is moved from charge receiving position forming `an end portion of the solidiflcation chamber.

8. Gas solidication and pressing apparatus including, spaced vertically disposed gas solidification and collecting chambers, a supporting structure for said chambers providing a vertically disposed solidified gas charge receiving chamber positioned intermediate and spaced from said solidiflcation chambers, said supporting structure forming a guideway between said sober, a movable transfer unit for each solidication chamber mounted in said guideway and providing a vertical charge transfer chamber therethrough, and each of saidunits movablein the guideway between charge receiving position below and in vertical prolongation of a solidication chamber and position above and vertically alined with said charg'e receiving chamber for, discharge thereinto.

9. Gas solidiflcation and pressing apparatus including, spaced vertically disposed gas solidification and collecting chambers, a `supporting structure for said chambers providing a guideway across and between the lower ends thereof and having spaced upper and lower walls, a vertically disposed solidified gas charge receiving and holding chamber formed `with its upper end opening through thelower wall of said guideway and spaced below and intermediate the lower ends of the solidifcation chambers, a transfer unit for each solidication chamber providing an chamber therethrough mounted in said guideway and normally positioned in alinement with and forming the lower end portion of a solidication chamber for receiving a charge therefrom, each of said units movablein the guideway between such normal position at its solidiiication chamber to a position at and alined with said charge holding chamber for discharging a charge into the latter chamber, said transfer units closed by the walls of the guideway during movements between tions, means for closing the lowerend off each solidification chamber when its transfer unit .is moved therefrom, and means for selectively actuating said transfer units. I f

1 0. A method of producing solid carbon dio ide in the form of snow which includes the'steps'fbff; reducing the pressure of liquid carbon dioxide to a. pressure close to but definitely above its triple point pressure prior to further expansion of the liquid for solidication; expanding such-reduced pressure liquid down to a pressure near'to'but definitely below the triple point pressure of carbon dioxide in a chamber closed to atmosphere;

and maintaining such below triple point pressure in the chamber by withdrawing the gaseous carbon dioxide from the chamber during vexpansionl of the liquid carbon dioxide in the chamber.

11. A method of solidifying carbon dioxide in the formV of snow, which includes the steps of; supplying liquid carbon dioxide at a gauge pressure of the order of approximately. 8 latmospheres 12. A method of producing solid carbon dioxide .in the form of' relatively loose crystals or snow,

which method includes the steps of; supplying liquid carbon dioxide at a pressure near to but definitely above the triple point pressure of carbon dioxide to a chamber closed to atmosphere; expandingv such liquid carbon dioxide in the chamber to a pressure below but definitely near to the triple point to convert a portion of the liquid lidication chambers across s'aid receiving chamto relatively loose and light crystal orsnow form and a portion of the liquid to gaseous form; and during expansion of the liquid in the chamber and productionl of the snow crystals therein, withdrawing the gaseous carbon dioxide from the chamber at a rate to maintain the pressure in the chamber to which the liquid is expanded near to but definitely belowthe triple point, whereby to lower gas velocity and reduce entrainment of the snow crystals with the withdrawn gases.'

13. In apparatus for pressing a solidified gas, including in combination and operative assembly separate'sources of solidified gas, a pressing unit for receiving and pressing charges of solidified gas from said' sources into blocks, and a separate' means for each solidified gas source for transferring charges of solidified gas therefrom to said pressing unit.

142 An apparatus for pressing a solidified gas. the combination and operative association of separate sources of solidified gas, a pressing unit including a pressing .chamber for receiving charges of solidified gas fromsaid sources, a separate means for transferring charges of solidified gas from each source to the pressing chamber of said pressing unit, and means for selectively'causing said charge transferring means to transfer charges from the respective sources .to the pressing uri-it.

. 15. An apparatus for pressing a solidified gas into blocks, including in combination and operative assembly separate sources of solidified gas, a pressing unit including a pressing chamber for receiving and in vwhich a charge is pressed into a :sol

block,' said pressing unit including means for ejecting a completed block therefrom, and means for transferring charges of solidified gas from anyv one of said sources-to the pressing chamber of said unit. v y

16. In gas solidification and pressing apparatus, a gas solidication chamber, a press unit having a solidified gas receiving and pressing .chamber spaced from said solidification chamber, a transfer unit for receiving a charge of solidified sas from the solidication chamber, said transfer unit in charge receiving position forming a porltion of the solidiiication chamber and movable from the chamber to a position for discharging the charge to the pressing chamber of the press unit, and means controlled by the transfer unit for closing the solidification chamber when said transfer unit is moved from charge-receiving position.

17. Gas solidication and pressing apparatus including, a vertically disposed gas solidication and collecting chamber, a supporting structure for said chamber providing a vertically disposed solidified gas charge-receiving chamber positioned spaced from said solidified chamber, said supporting structure forming a guideway from said solidii'lcation chamber to and across said receiving chamber, a movable transfer unit mounted in said guideway and providing a. vertical charge transfer chamber therethrough, and the said transfer unit movable in the guideway between charge-receiving position below and in vertical prolongation of' the solidification chamber and a position above and vertically alined with said charge-receiving chamber for discharge thereinto.

18. An apparatus for gas solidification and pressing, including in operative combination; separate gas solidication chambers, a press unit including a solidified gas pressing chamber having a pressing plunger therein, and transfer units movable between positions at and in gas-tight charge-receiving communication with said solidication chambers, respectively, and a position in gas-tight charge-discharging communication "with said press unit for transferring charges of y solidified gas from the solidiiication chambers to the pressing chamber of the press unit. y

19. In apparatus for gas' solidiflcation and 'gas-tight communica-tion with and for receiving a charge of solidified gas from the solidification chamber, and a position in gas-tightl communication with said charge-holding chamberfor discharging such charge into said holding chamber.

20. In gas solidiflcation and pressing apparatus, the combination of, a gas solidification chamber, a press unit having a pressing chamber spaced from said solidification chamber for receiving a charge of solidified gas and for pressing such a charge into a block, and a solidified gas charge transfer unit movable between a position in gas-tight communication with the solidiiication chamber to receive a charge of solidified gas from said chamber, and a position in gas-tight communication with` the pressing chamber of the press unit for discharging the charge of y solidified gas to said pressing chamber.

l21. In apparatus for pressing a solidified gas, in combination, separate sources of solidified gas, a pressing unit for receiving and pressing charges of solidified gas from said sources into blocks, separate means for each solidified gas source for transferring charges of solidified gas therefrom to said pressing unit, and each of said charge-transferring means being constructed with its respective solidied gas source and for gas-tight communication with said pressing unit. 22. In apparatus for pressing a solidified gas, in combination, a source of solidied gas, a pressing unit for receiving and pressing charges of solidied gas from said source into blocks, and means for transferring charges of solidified gas from said sourceI to said.. pressing unit, the said means being constructed and arranged for gastight communication with said source andfor gas-tight communication with said pressing unit and also being designed to maintain a charge of solidified gas therein sealed from the atmosphere during transfer from said source to said unit.

23. A unitary apparatus for gas solidiiication and'A pressing, including in operative `combination, separate sources of solidified gas, a pressing unitv including a pressing chamber for pressing charges of solidifiedgas from said sources into blocks, and means for transferring a charge of solidified gas from any one of said sources to the press unit for discharge of the charge from said means into the pressing chamber of saidV gas solidification chambers, a solidified gasV charge-receiving chamber spaced from said solidification chambers, means for transferring a charge of solidified gas from any one of said solidication chambers to said receiving chamber, and a solidified gas pressing unit havingA a pressing chamber for operative association with said. charge-receiving chamber to receive a charge of solidified gas from said receiving chamber.

25. In apparatus for gas solidiiication and pressing,` in combination, a source of solidified gas, a chamber spaced from said source for receiving and holding a charge of solidified gas, a solidified gas pressing chamber for recevinga charge 'of solidified gas from said charge holding chamber, and a transfer unit movable between a position receiving a charge of solidified gas from said source and a' position discharging such charge into the charge-holding chamber.

26. A unitary gas solidification and pressing apparatus, including, in combination, a gas solidication chamber, a pressing chamber spaced 

